This invention relates to a coin sorting machine in which a sorting coil is arranged along a coin passage, and the characteristics of coins are determined by a sorting means employing the sorting coil, to thereby sort out coins inserted thereinto. More particularly, the invention is related to a device for preventing an erroneous coin counting operation which may be caused by a real coin inserted thereinto with a string attached.
For instance, in a coin sorting device for an automatic vending machine, a sorting coil is provided along a coin passageway, and the characteristics of coins are determined by a sorting means employing the sorting coil. There are typically three different sorting means. In a first sorting means, a bridge circuit is made up of a sorting coil and a reference impedance coil and the balance of the bridge circuit occurring when a coin passes through the sorting coil is detected. In a second sorting means, an oscillation coil and a reception coil are provided to serve as sorting coil, and the variation of the voltage induced in the reception coil when a coin passes through the oscillation coil is detected. In a third sorting means, an oscillator having a sorting coil as its resonance element is provided, and the variation of the oscillation frequency of the oscillator caused when a coin passes through the sorting coil is detected. In each of these sorting means, when an inserted coin passes through the sorting coil, a sorting signal indicating whether it is a true coin and a false coin is outputted, and simultaneously a coin counting signal is provided.
In a machine of this type, unlike the mechanical type coin sorting machine, there are no obstructive components such as a cradle and a carrier arm for determining the diameter of a coin and, accordingly, the number of components can be reduced. However, since a coin inserted in the coin inlet can roll along the coin passage without being obstructed by anything, it is readily possible to move the coin back to the coin inlet. In other words, if a real coin tied with a string is inserted into the coin inlet out of mischief, the coin can be moved back to the coin inlet by pulling the string tied to the coin. In this case, the coin count value is undoubtedly incorrect.
In order to eliminate this trouble or drawback, a device for preventing an inserted coin from being moved back has been provided at the coin inlet. In this case, at least it is possible to prevent an inserted coin from being moved all the way back to the coin inlet; however, limited movement of the coin is still possible and a noticeable error is produced in the coin count value. If the inserted coin is reciprocated through the coin sorting section several times by operating the string tied to the coin, the error in the count value is increased as much.